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IFI6 Inhibits Apoptosis via Mitochondrial-Dependent Pathway in Dengue Virus 2 Infected Vascular Endothelial Cells.

Qi Y, Li Y, Zhang Y, Zhang L, Wang Z, Zhang X, Gui L, Huang J - PLoS ONE (2015)

Bottom Line: Interferon (IFN)-stimulated genes (ISGs) induced by dengue virus (DENV) exert antiviral effects.We observed that Bcl-2 expression was increased in IFI6+/+ and decreased in IFI6-/- cells.By contrast, Bax expression was decreased in IFI6+/+ and increased in IFI6-/- cells.

View Article: PubMed Central - PubMed

Affiliation: Institute of Immunology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, PR China; Key Laboratory of Tropical Diseases Control, Ministry of Education, Guangzhou, PR China.

ABSTRACT
Dengue hemorrhagic fever (DHF)/Dengue shock syndrome (DSS) is a fatal infectious disease that demands an effective treatment. Interferon (IFN)-stimulated genes (ISGs) induced by dengue virus (DENV) exert antiviral effects. Among ISGs, IFN-α inducible gene 6 (IFI6) was increased in DENV infected human umbilical vascular endothelial cells (HUVECs) by microarray analysis in our previous study. However, its function is incompletely understood. In this study, we confirmed that IFI6 was markedly induced in DENV infection of both primary HUVECs and EA.hy926 cell lines. Recombinant EA.hy926 cell lines in which IFI6 was either over-expressed (IFI6+/+) or knocked-down (IFI6-/-) were generated. The activation of caspase-3 and intrinsic apoptosis-related protein caspase-9 were down-regulated in IFI6+/+ but up-regulated in IFI6-/- cells at 24-48 hrs post-infection. After incubation with DENV for 48 hrs, the mitochondrial membrane potential (Δψ(m)) was more stable in IFI6+/+ cells but reduced in IFI6-/- cells, as assayed by fluorescence staining with JC-1. We observed that Bcl-2 expression was increased in IFI6+/+ and decreased in IFI6-/- cells. By contrast, Bax expression was decreased in IFI6+/+ and increased in IFI6-/- cells. It is presumed that the anti-apoptotic function of IFI6 is expressed by regulating the rheostatic balance between bcl-2/bax expression and inhibition of Δψ(m) depolarization during DENV infection of vascular endothelial cells(VECs). In addition, the pro-apoptotic protein X-linked Inhibitor of Apoptosis (XIAP)-Associated Factor 1(XAF1) expression had been reported to be up-regulated and led to the induction of apoptosis in DENV2-infected VECs,but the relationship between XAF1 and IFI6 dengue virus-induced apoptosis in VECs warrants further study.

No MeSH data available.


Related in: MedlinePlus

IFI6 ihibits the expression of caspase-3/caspase-8 and the activity of caspase-9.(a and b) Immunoblotting was used to detect the expressions of caspase-3 and caspase-8 in IFI6+/+ cell lines and IFI6-/- cell lines that were infected by DENV2 (MOI = 4) for 24, 36 and 48 hrs, respectively. (c and d) The activity of caspase-9 was analyzed using a colorimetric assay. The results shown were from three independent experiments. ***P<0.01.
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pone.0132743.g004: IFI6 ihibits the expression of caspase-3/caspase-8 and the activity of caspase-9.(a and b) Immunoblotting was used to detect the expressions of caspase-3 and caspase-8 in IFI6+/+ cell lines and IFI6-/- cell lines that were infected by DENV2 (MOI = 4) for 24, 36 and 48 hrs, respectively. (c and d) The activity of caspase-9 was analyzed using a colorimetric assay. The results shown were from three independent experiments. ***P<0.01.

Mentions: To determine whether intrinsic or extrinsic pathways were activated during apoptosis induced by DENV2 infection, we detected protein levels of caspase-3 and 8 using immunoblotting and anzyme activity of caspase-9 using colorimetry. As shown in Fig 4a, stronger inhibition of cleaved caspase-3 occurred time-dependently in IFI6+/+ cells as compared with vector-high cells. By stark contrast, an extremely increased level of cleaved caspase-3 was observed in IFI6-/- cells as compared with vector-low cells (Fig 4b). Caspase-8 was expressed at much lower levels at the early stages of DENV2 infection in IFI6+/+ cells as compared with vector-high cells, but there was no marked difference at 48 hrs post-infection. Additionally, increased tendency of caspase-8 activation was also inconspicuous in vector-low cells (Fig 4a and 4b). However, consistent lower activity of caspase-9 was observed in IFI6+/+ cells as compared with vector-high cells (Fig 4c) while much higher activity of caspase-9 was observed in IFI6-/- cells as compared with vector-low cells (Fig 4d).


IFI6 Inhibits Apoptosis via Mitochondrial-Dependent Pathway in Dengue Virus 2 Infected Vascular Endothelial Cells.

Qi Y, Li Y, Zhang Y, Zhang L, Wang Z, Zhang X, Gui L, Huang J - PLoS ONE (2015)

IFI6 ihibits the expression of caspase-3/caspase-8 and the activity of caspase-9.(a and b) Immunoblotting was used to detect the expressions of caspase-3 and caspase-8 in IFI6+/+ cell lines and IFI6-/- cell lines that were infected by DENV2 (MOI = 4) for 24, 36 and 48 hrs, respectively. (c and d) The activity of caspase-9 was analyzed using a colorimetric assay. The results shown were from three independent experiments. ***P<0.01.
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4526556&req=5

pone.0132743.g004: IFI6 ihibits the expression of caspase-3/caspase-8 and the activity of caspase-9.(a and b) Immunoblotting was used to detect the expressions of caspase-3 and caspase-8 in IFI6+/+ cell lines and IFI6-/- cell lines that were infected by DENV2 (MOI = 4) for 24, 36 and 48 hrs, respectively. (c and d) The activity of caspase-9 was analyzed using a colorimetric assay. The results shown were from three independent experiments. ***P<0.01.
Mentions: To determine whether intrinsic or extrinsic pathways were activated during apoptosis induced by DENV2 infection, we detected protein levels of caspase-3 and 8 using immunoblotting and anzyme activity of caspase-9 using colorimetry. As shown in Fig 4a, stronger inhibition of cleaved caspase-3 occurred time-dependently in IFI6+/+ cells as compared with vector-high cells. By stark contrast, an extremely increased level of cleaved caspase-3 was observed in IFI6-/- cells as compared with vector-low cells (Fig 4b). Caspase-8 was expressed at much lower levels at the early stages of DENV2 infection in IFI6+/+ cells as compared with vector-high cells, but there was no marked difference at 48 hrs post-infection. Additionally, increased tendency of caspase-8 activation was also inconspicuous in vector-low cells (Fig 4a and 4b). However, consistent lower activity of caspase-9 was observed in IFI6+/+ cells as compared with vector-high cells (Fig 4c) while much higher activity of caspase-9 was observed in IFI6-/- cells as compared with vector-low cells (Fig 4d).

Bottom Line: Interferon (IFN)-stimulated genes (ISGs) induced by dengue virus (DENV) exert antiviral effects.We observed that Bcl-2 expression was increased in IFI6+/+ and decreased in IFI6-/- cells.By contrast, Bax expression was decreased in IFI6+/+ and increased in IFI6-/- cells.

View Article: PubMed Central - PubMed

Affiliation: Institute of Immunology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, PR China; Key Laboratory of Tropical Diseases Control, Ministry of Education, Guangzhou, PR China.

ABSTRACT
Dengue hemorrhagic fever (DHF)/Dengue shock syndrome (DSS) is a fatal infectious disease that demands an effective treatment. Interferon (IFN)-stimulated genes (ISGs) induced by dengue virus (DENV) exert antiviral effects. Among ISGs, IFN-α inducible gene 6 (IFI6) was increased in DENV infected human umbilical vascular endothelial cells (HUVECs) by microarray analysis in our previous study. However, its function is incompletely understood. In this study, we confirmed that IFI6 was markedly induced in DENV infection of both primary HUVECs and EA.hy926 cell lines. Recombinant EA.hy926 cell lines in which IFI6 was either over-expressed (IFI6+/+) or knocked-down (IFI6-/-) were generated. The activation of caspase-3 and intrinsic apoptosis-related protein caspase-9 were down-regulated in IFI6+/+ but up-regulated in IFI6-/- cells at 24-48 hrs post-infection. After incubation with DENV for 48 hrs, the mitochondrial membrane potential (Δψ(m)) was more stable in IFI6+/+ cells but reduced in IFI6-/- cells, as assayed by fluorescence staining with JC-1. We observed that Bcl-2 expression was increased in IFI6+/+ and decreased in IFI6-/- cells. By contrast, Bax expression was decreased in IFI6+/+ and increased in IFI6-/- cells. It is presumed that the anti-apoptotic function of IFI6 is expressed by regulating the rheostatic balance between bcl-2/bax expression and inhibition of Δψ(m) depolarization during DENV infection of vascular endothelial cells(VECs). In addition, the pro-apoptotic protein X-linked Inhibitor of Apoptosis (XIAP)-Associated Factor 1(XAF1) expression had been reported to be up-regulated and led to the induction of apoptosis in DENV2-infected VECs,but the relationship between XAF1 and IFI6 dengue virus-induced apoptosis in VECs warrants further study.

No MeSH data available.


Related in: MedlinePlus